Umm, really not trying to come across like a jerk or troll or anything, but I guess I'm confused. Is this supposed to keep out cars or larger vehicles? I'm not understanding how those are supposed to stop a bike.

They're for keeping moto and horses out. Once the barriers are build along the sides, you can try to ride though it while rotating your pedals so you don't hit the pipes in the center. They're not easy to ride through and I found putting a foot on it while passing is the easiest. Pic is out of scale, the taller pipe is probably 3' tall. I have only seen this on the olympic discovery trail.